1. Field of the Invention
The invention concerns a device for measuring an electric field comprising at least one optical fiber sensor which has at least one piezoelectric sensor element that detects with the aid of the inverse piezoelectric effect a predetermined directional component, assigned to it, of the electric field, as well as first means that generate a sensor signal corresponding in each case to the assigned directional component.
2. Discussion of Background
Conventional optical and optical fiber sensors for measuring electric fields are based predominantly on electrooptic effects (Pockels effect, Kerr effect). Optical fiber sensors based on the inverse piezo effect have recently been developed. These known sensors generate a signal which is proportional to the field strength. However, with the known optical fiber sensors it is not possible simultaneously to detect the direction and absolute value of an electric field. Rather, the field direction must be known in advance, so that the field strength can be determined.
A short while ago, an optical fiber sensor was disclosed (e.g. Swiss Patent Application CH-1628/88-2), which exclusively detects a predetermined directional component of the field. The directional component is determined by the shape and the design of the sensor, and easily recognizable at the sensor (e.g. surface normal of a disk-shaped sensor wafer).
Optical fiber sensors have the basic advantage that they are insensitive to electrical and magnetic disturbances. Moreover, because of their insulating properties they can be used in the presence of large electric voltages without any problems. Today, the interferometric detection needed with optical fiber sensors is at a high technical level. This is illustrated by the following list of relevant printed publications:
"Fiber-optic Fabry-Perot Interferometer and its Sensor Application", T. Yoshino et.al. IEEE J. of Quant. Electr. QU-18, page 1624, 1982, PA1 "Electric Field Sensitive Optical Fibre Using Piezoelectric Polymer Coating)", L. J. Donalds et.al. Electr. Lett 18, page 327, 1982, PA1 "Strain effects on highly elliptical core two-mode fibers", J. N. Blake et.al., Optics Letters Vol. 12 No. 9, page 732 et seq., 1987, PA1 "Use of highly elliptical core fibers for two-mode fiber devices", B. Y. Kim et.al., Optics Letters Vol. 12 No. 9, page 729 et seq., 1987.